Conventionally, tissue specimens are prepared for microtome sectioning in two sequential stages. In the first stage, the tissue specimen is placed in a cassette and processed by solvents which remove the water content of the specimen. The specimen is removed from the cassette and subjected to the second stage, called embedding, which involves placing the specimen in a small dish which is then filled with molten wax. This wax impregnates and surrounds the specimen which is thus embedded in wax. The embedded specimen is then removed from the dish and the wax block is mounted in the clamp of a microtome for sectioning of the specimen. It is important that the specimen is accurately positioned in the dish prior to the wax setting around the specimen, so that sectioning of the specimen occurs along the appropriate planes to reveal the desired cell structure. In the past, this positioning has been achieved by allowing a few drops of molten wax to fall into the base of the otherwise empty dish, allowing the resulting small quantity of wax partially to set and to position the specimen in the plastic wax in the desired orientation using tweezers. This holds the specimen in the required position, after which more molten wax is added to the container, to fully embed the specimen.
In one aspect the invention aims to provide a cassette, and a method of using a cassette, wherein a tissue specimen can be accurately and precisely located and oriented in the cassette prior to embedding of the cassette in the embedding medium.
In another aspect the invention is concerned with embedding a plurality of specimens simultaneously in a container. Hitherto this has been done by placing the cassettes in a container into which molten wax is introduced to a depth sufficient to cover the cassettes. The wax is then caused or allowed to cool, but the problem of removal of the cassettes from the solidified block of wax then presents itself.